be2net: Support vxlan offload stats in the driver

This patch adds vxlan offload specific counters to ethtool stats. We
provide tx/rx queue counters to show the number of vxlan offload pkts
sent/received.

Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>